To the original poster - 

What are your great grandmother's names on her gravestone, in English and in Hebrew/Yiddish? Those should provide some useful information. 

Here in the US, did she go by Kuna in everyday life and is that her name on census records?

Also - was she getting a visa at the US consulate in Riga?
--
Michele Lock

Lock/Lak/Lok and Kalon in Zagare/Joniskis, Lithuania
Olitsky in Alytus, Suwalki, Poland/Lithuania
Gutman/Goodman in Czestochowa, Poland
Lavine in Trenton, New Jersey and Lida/Minsk gub., Belarus